This should be a pretty simple upgrade. You already have SQL backups but a final backup would be good. Snapshot your two AppSense servers. Run the installer to upgrade the suite on one of the servers. During this time that server will go offline and users will fail to the other server. Once the upgrade is completed you will need to upgrade the schema of the databases using the Server Configuration Portal. Once this is done from the first server it will come online and the second will go offline due to a schema mismatch. Upgrade the components on the second server.

Once all that is done you can upgrade configs and agents at your leisure.

Page 62 and also 79 on of the Install and Configure Guide cover this in detail.